Anticipated Flows in Gunny Gorge -- May/June
I attended yesterday's (4/24/2014) Aspinall operations meeting (see attached handout). The flows this year are very likely to be managed really differently than any previous season. The Bureau of Reclamation (BOR) is operating under their Record of Decision (ROD) from an Environmental Impact Statement (EIS) that they've spent the last several years developing. It is now signed, final and in effect. They were operating under the ROD last year, but because of the very poor run-off situation there was not much impact from it on recreational river use.
This year however, things are way different. This year we are at the high end of an "average wet" scenario for inflows into Blue Mesa Reservoir, with an inflow forcast of 850,000 acre feet. That triggers flow obligations on the part of BOR that will siginficantly affect recreational use on the Gunnison River downriver from Crystal Dam, likely from mid-May through June. The flow targets are designed to benefit threatened and endangered warm water fish species.
(see page 25 of attachment)
According to the ROD, releases under the current inflow forcast have to be managed to deliver 14,450 cfs to Whitewater for a duration of 10 days. Also required is the delivery of 8,070 cfs at Whitewater for 40 days. So BOR will be releasing enough water from Crystal Dam through Black Canyon and Gunnison Gorge to make up for whatever is needed in excess of the runoff from the North Fork, Uncompahgre River, and the few downriver side drainages that add a bit to flows during spring runoff. According to the runoff forcasts, releases from Crystal Dam will need to be pretty big to accomplish this.
Here's a scenario that is likely. The black line on the graph represents flows through the Gunnison Gorge in the scenario.
(see page 32 of attachment)
The timing of the releases is weather-dependent, and will be timed to match peak runoff of the North Fork and Cimarron Rivers. So that may change from what you see on the graph. It may happen a bit earlier or a bit later than the dates on the graph. But from what I learned yesterday, I would expect that the magnitude and duration of the releases from Crystal to pretty closely match the graph above. If so, it will have big impacts to May/June fishing.
On the other hand, it will make for some high-flow boating opportunities in the Gunnison Gorge and nice sporty flows on the Lower Gunnison. Could be a good year for multi-day raft trips from Gunnison Forks (near the Pleasure Park) to Whitewater.
I have not mentioned the 24 hour peak flow for the Black Canyon water right because the 10-day peak will exceed this year's Black Canyon target of 6,400 cfs. Therefore, it's a moot point.
Crystal Dam will spill this year. Morrow Point Dam will probably spill, and Blue Mesa Dam may need to spill to deliver the required flows.
Blue Mesa Reservoir is expected to fill this summer.